US Signal Jammers vs Remotely Detonated IEDs

Afghan militants began attacking U.S. troops with improvised explosive devices in the first days after the October 2001 invasion. By early ‘02, al-Qaida bomb-makers were cramming radio frequency receivers and simple digital signal decoders into the bases of Japan InstaLite fluorescent lamps. Then they’d connect the two-and-a-half inch wide lamp bases to firing circuits, and to Soviet-era munitions. The result was a crude, radio-controlled weapon dubbed the “Spider” by the Americans. With it, an attacker could wait for his prey, set off the bomb at just the right moment — and never have to worry about getting caught. When the explosion happened, he’d be hundreds of yards away.

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Meanwhile, the Army looked for ways to modify its Shortstop Electronic Protection System, designed to shield troops from artillery and mortar fire. This was a so-called “reactive” countermeasure. It monitored the airwaves, listening for one of the radio signals used by the munitions’ proximity fuses. Once the countermeasure heard that signal, Shortstop recorded it, modified it, and then blasted it back at the munition. By confusing the weapons with their own signals, Shortstop could fool the shells into prematurely detonating.

The soldiers tweaked the Shortstop to scan for radio-controlled bombs’ triggering frequencies, and to rely on a Humvee’s power supply. “The wife of one Fort Monmouth engineer collected miniature kitchen witches that inspired a new name for the device: Warlock Green,” Atkinson recounts.

Five Warlock Greens accompanied U.S. forces into Iraq in March, 2003. By mid-summer, there were 100 jammers in the warzone. It wasn’t nearly enough. Iraq’s militants had learned from their compatriots in Afghanistan, and were setting off remotely-detonated explosives everywhere.

Just like the first turn of this improvised explosive device (IED) war, the electronic countermeasures were having trouble keeping up with the bombs.

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“Every time we put a countermeasure in the field – especially with Warlock – they were able to outstrip it,” says Paul Mueller, a long-time defense executive, who supervised jammer-building operations at EDO and at the ITT Corporation. “They were a step ahead of us.”

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In the early fall of 2004, the Army signed a contract for 1,000 Warlocks. By March, 2005, the Army upped that order to 8,000 jammers. It was a high-tech, electromagnetic surge. And it was meant to send the militants sliding back down the scale of sophistication. “If somebody can sit a click [kilometer] away with a radio and target our guys, we’ve got almost no ability to get him,” says a source familiar with the jammer buildup. “But if he’s doing the Wile E. Coyote thing, and pushing down that plunger, at least we’ve got some chance to shoot him before he gets it down.”

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Even more secret were the flights of the jammers in the sky. The Navy’s EA-6 Prowlers could not only block triggering signals; they could remotely detonate the bombs, as well. But they had to be very, very careful. U.S. vehicles equipped with jammers had to get off of the roads, or risk the deadliest embrace of all. Pilots had to make sure that civilians were nowhere nearby, when they set the bombs off.

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…our Humvee rolled over an artillery shell, buried in the highway’s middle lane and wired to a radio. An improvised bomb.

The IED didn’t go off, for reasons that weren’t completely clear. The Death X bomber might have gotten cold feet. More likely, one of Warlocks in the Humvee prevented him from detonating the weapon.

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2006 rolled on. The insurgency in Iraq got worse. Much worse. The number of troops wounded by bombs hit 15,000, and kept going. Explosively formed projectiles — bombs that shot out jet of molten, armor-piercing metal — went from a macabre curiosity to something like a staple of the insurgent arsenal. There seemed to be no end to the carnage.

Militant bombmakers increasingly turned to long range cordless telephones and cell phones for their triggers. That was a serious issue. The digital devices were built to overcome dropped packets, reflected signals, and transmission errors. Warlock Green’s trick of fooling a trigger with its own, modified signal didn’t work. The gadgets were used to the hiccups.

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By the time I returned to Iraq, in the summer of 2007, IEDs had become relics in broad swaths of the country. The insurgents had largely abandoned their tool of choice.

It was not altogether good news.

North of Baghdad, insurgents took insulated copper threads, some not much thicker than a hair, and buried them in the dust. Then they strung them out for as long as a kilometer. At one end was an insurgent triggerman. At the other, an explosively formed projectile. It was a crude approach to killing — even more primitive than those first bombs planted in Afghanistan. But it was lethally effective.

These “command wire” bombs had a fatal flaw, however. Insurgents had to stick around to set them off. That made them vulnerable to American counter-attacks and preemption. And that brought the number of bombs and bomb fatalities way down. In December of 2007, only nine U.S. troops were killed by IEDs, and another 166 were wounded. It was still an awful toll. But it was a tiny fraction of the 69 slain and 473 injured in December of 2006.

The casualty figures continued to fall as the military began to field a third generation countermeasure — one that could stomp out a huge swath of radio triggers with all sorts of jamming techniques.

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In the broadest sense, the strategy behind the U.S. jammer buildup had succeeded. Thanks to the Americans’ bleeding edge technologies, the militants had dropped back down the ladder of sophistication. They were now taking the Wile E. Coyote approach — pushing down the plunger to detonate the bomb — and suffering for it. “That was the whole intent of the program: pushing the enemy back to archaic means,” says a source familiar with the effort. “So they’d actually have to face you and fight you.”

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In Afghanistan, however, the terrain favored the low tech. All the gadgets the Americans had bought and built for Iraq proved largely worthless against a new slew of throwback threats. The bombs were largely made of wood and fertilizer, making them practically invisible to metal detectors. No command wires were needed to set them off; just the pressure of an unlucky boot. The placement of the bombs added to their effectiveness. The U.S. military’s new hard-shelled, blast-deflecting vehicles were built for Iraq’s well-paved roads. So the insurgents put their explosives in the gullies and the mud paths, where the trucks were useless. The bomb-handling robots couldn’t handle the rough terrain, either. And, during the summer, the weather was so hot, EOD technicians didn’t even bother wearing their protective suits.

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But one thing is for sure: it’s a long way from stopping crude triggers, stuffed into disposable lamps. It’s a long way from frantically tweaking electronics in the hope of somehow keeping thirty soldiers a day from being blown up. It’s a long way from the near decade-long fight against remote-controlled bombs in which the enemy had the advantage of being the first mover. This may be the chance to get ahead, before the next wave of terror weapons hits.